Oganesson

NOBLE GAS · GROUP 18 · PERIOD 7
118
Og
Oganesson
294

Atomic Data

Atomic Number118
SymbolOg
Atomic Weight294 u
Density (STP)N/A
Melting PointN/A °C (None K)
Boiling PointN/A °C (None K)
Electronegativity:
Electron Config.1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 5f14 6s2 6p6 6d10 7s2 7p6
Oxidation States0, +2, +4, +6
Phase at STPSolid
CategoryNoble Gas
Period / Group7 / 18
CAS Number54144-19-3

Electron Configuration

[Rn] 5f14 6d10 7s2 7p6

Shell n Subshell Electrons Cumulative
K11s22
L22s24
L22p610
M33s212
M33p618
M33d1028
N44s230
N44p636
N44d1046
N44f1460
O55s262
O55p668
O55d1078
O55f1492
P66s294
P66p6100
P66d10110
Q77s2112
Q77p6118
Total 118 118

Isotopes of Oganesson

Oganesson is monoisotopic: ²⁹⁴Og is its only naturally occurring stable isotope, accounting for 100% of all natural Oganesson.

Isotope Symbol Protons Neutrons Abundance Stability
Oganesson-294²⁹⁴Og118176traceStable

Abundance & Occurrence

Oganesson is present in Earth's crust at approximately trace amounts by mass and at approximately trace amounts by mass throughout the universe.

Earth's Crust (ppm by mass)

Oganesson
None ppm
Silicon (ref.)
277,000 ppm
Oxygen (ref.)
461,000 ppm

Universe (ppm by mass)

Oganesson
None ppm
Helium (ref.)
230,000 ppm
Hydrogen (ref.)
739,000 ppm

Discovery & History

2002
Yuri Oganessian et al. (JINR, Dubna / Lawrence Livermore): Oganesson was synthesised by bombarding californium-249 with calcium-48 ions, producing three atoms of Og-294 (t½ ≈ 0.89 ms); it is the heaviest element confirmed to date and the only synthetic member of the noble gas group.
2015
JINR / Lawrence Livermore confirmation: Additional atoms of Og-294 were produced to meet IUPAC discovery criteria; relativistic calculations suggest oganesson may be a solid at room temperature and chemically reactive: unlike lighter noble gases: due to extreme electron orbital contraction.
2016
IUPAC: IUPAC named element 118 oganesson in honour of physicist Yuri Oganessian, whose calcium-48 bombardment technique enabled the discovery of elements 113–118 and whose contributions to superheavy element research span six decades.

Read more about the discovery of the periodic table of elements →

Safety & Handling

  • Alpha radiation and very short half-life: Oganesson's only known isotope, Og-294 (t½ ≈ 0.89 ms), decays in under a millisecond; only five atoms have ever been detected, and no chemical characterisation has been possible.
  • No practical hazard: Oganesson exists only in atom-counting experiments; there is no macroscopic radiological, chemical, or toxicological hazard from the element itself.
  • Californium target radiation: Synthesis requires californium-249 targets, which are intense neutron and alpha sources; target handling is conducted remotely in shielded hot cells at licensed nuclear facilities.
  • Regulatory controls: All oganesson experiments are conducted at the JINR Dubna facility and Lawrence Livermore National Laboratory under comprehensive nuclear regulatory and safeguards frameworks.

Real-World Uses

  • Heaviest known element: Oganesson (Og-294) is the heaviest confirmed element, the last member of Period 7, and closes the noble gas group (Group 18); its synthesis in 2002 at JINR Dubna represents the current frontier of experimental nuclear science.
  • Predicted non-noble-gas behaviour: Relativistic calculations indicate that oganesson's 7p electrons are so strongly affected by relativistic effects that its electron shell is nearly spherically symmetrical, and it may not behave as a chemically inert noble gas: possibly being a solid semiconductor at room temperature rather than a gas.
  • No commercial applications: Only about 5 atoms of oganesson have ever been detected; Og-294 has a half-life of about 0.7 milliseconds, making any application utterly impossible with current or foreseeable technology.

Downloadable Resources

Free periodic table reference sheets for classrooms, study sessions, and laboratory use.

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Frequently Asked Questions

Has oganesson ever been used for anything?

No. Oganesson has no practical applications. Its most stable isotope (Og-294) has a half-life of about 0.7 milliseconds: less than one thousandth of a second. Only a handful of atoms have ever been produced. Oganesson is the heaviest element currently on the periodic table and the end of period 7, making it a noble gas by position: though relativistic effects may mean it behaves very differently from noble gases.

How many atoms of oganesson have been made?

As of 2025, only five atoms of oganesson have ever been confirmed: three in the original 2002 synthesis at JINR Dubna and two in a confirmatory experiment in 2005. Each existed for less than a millisecond before decaying. Oganesson is the rarest element ever created and the current end of the periodic table.

Is oganesson a noble gas?

Oganesson occupies the position of a noble gas in Group 18 of the periodic table (below radon), but relativistic quantum mechanical calculations predict it may not behave like one. Its 7p electrons are predicted to be far more reactive than those of lighter noble gases, and some calculations suggest oganesson might actually be a solid at room temperature with a small bandgap: more like a semiconductor than an inert gas. This can likely never be tested given that only a handful of atoms exist for fractions of a millisecond.

How did oganesson get its name?

Oganesson was named after Yuri Oganessian, the Russian-Armenian nuclear physicist who pioneered the use of calcium-48 beams for synthesising superheavy elements and led or contributed to the discovery of elements 104 through 118 at JINR Dubna. It is only the second element named after a living person (after seaborgium, named after Glenn Seaborg while he was alive). The name was approved by IUPAC in 2016.